Herb and Spices in Colorectal Cancer Prevention and Treatment: A Narrative Review

Colorectal cancer (CRC) is the second most deadly cancer worldwide. CRC management is challenging due to late detection, high recurrence rate, and multi-drug resistance. Herbs and spices used in cooking, practised for generations, have been shown to contain CRC protective effect or even be useful as an anti-CRC adjuvant therapy when used in high doses. Herbs and spices contain many bioactive compounds and possess many beneficial health effects. The chemopreventive properties of these herbs and spices are mainly mediated by the BCL-2, K-ras, and MMP pathways, caspase activation, the extrinsic apoptotic pathway, and the regulation of ER-stress-induced apoptosis. As a safer natural alternative, these herbs and spices could be good candidates for chemopreventive or chemotherapeutic agents for CRC management because of their antiproliferative action on colorectal carcinoma cells and inhibitory activity on angiogenesis. Therefore, in this narrative review, six different spices and herbs: ginger (Zingiber officinale Roscoe), turmeric (Curcuma longa L.), garlic (Allium sativum L.), fenugreek (Trigonella foenum-graecum L.), sesame (Sesamum indicum L.), and flaxseed (Linum usitatissimum L.) used in daily cuisine were selected for this study and analyzed for their chemoprotective or chemotherapeutic roles in CRC management with underlying molecular mechanisms of actions. Initially, this study comprehensively discussed the molecular basis of CRC development, followed by culinary and traditional uses, current scientific research, and publications of selected herbs and spices on cancers. Lead compounds have been discussed comprehensively for each herb and spice, including anti-CRC phytoconstituents, antioxidant activities, anti-inflammatory properties, and finally, anti-CRC effects with treatment mechanisms. Future possible works have been suggested where applicable.

Colorectal Cancer
Cancer is a leading cause of death that significantly affects the life expectancy of every nation. Colorectal cancer (CRC) is the third most commonly diagnosed and second most deadly cancer globally (WHO, 2021) that accounting for approximately 9.39% of death of all recorded cancers in 2020 (Ferlay et al., 2020;Hossain et al., 2022). CRC incidence is expected to double by 2035 worldwide due to the fast acceleration of diagnosed cases in the elderly. Less developed countries are expected to rise in diagnosed cases of CRC (Papamichael et al., 2015;Hossain et al., 2022).
The term CRC is specific to the large intestine and rectum, where it develops from the abnormal growth of glandular epithelial cells. This development occurs when epithelial cells acquire a succession of genetic or epigenetic alterations that provide them with a selective advantage of hyper-proliferation (Testa et al., 2018). These out of control growing cells produce a benign adenoma, which then progresses to carcinoma and metastasis by three major pathways: microsatellite instability (MSI), chromosomal instability (CIN), and CpG island methylator phenotype (CIMP) (Vogelstein et al., 1988;Nguyen and Duong, 2018;Malki et al., 2020). Like any other tumour or cancer, CRC is classified into stages: Stage 0 (carcinoma in situ) to stage IV. Standard treatment options for the stages 0 -II CRC are surgery, whereas stage III requires surgery and adjuvant chemotherapy, and stage IV and recurrence CRC involve surgery, chemotherapy, and targeted therapy (PDQ, 2021).

Colorectal Cancer Treatment Opportunity and Challenges
Regular screening can prevent CRC. As a polyp takes 10-15 years to be cancerous, detecting and removing polyps at an early stage is critical. However, only 40% of CRC are found at early stages, and sometimes CRC recurs after treatment (ACS, 2020). For CRC treatment strategy, Food and Drug Administration (FDA) approved at least 30 different drugs (Supplementary Table  S1), and either singly or in combination with other drugs (Supplementary Table S2) are used for CRC treatment. These chemotherapeutic drugs are exposed to the cancer cells and simultaneously damage healthy cells. Consequently, these drugs manifest several adverse effects, including fatigue, headache, muscle pain, stomach pain, diarrhoea and vomiting, sore throat, blood abnormalities, constipation, neuronal damage, skin changes, memory problems, loss of appetite, and hair loss (ACS, 2020).
Even though the overall survival of individuals with advanced CRC has increased in recent decades due to new chemotherapy regimens (Supplementary Tables S1, S2); however, in nearly all patients with CRC, current systemic chemotherapies developed resistance (Cho and Hu, 2020), limiting the therapeutic efficacy of anti-cancer medicines and ultimately leading to chemotherapy failure. Chemotherapeutic drug resistance is a major issue in CRC treatment in the current clinical practice. Apart from this limitation, the access to diagnosis and treatment of CRC for survival is less accessible in developing countries, particularly for rural people, where about 44% of the world's people currently live (World Bank, 2021). Therefore, nearly half the world's population lacks the means to diagnose and treat.

Natural Remedies for Colorectal Cancer
According to World Health Organization (WHO), 75-80% of the world's population solely rely on traditional medical systems for their first line of treatment due to concerns about the safety and efficacy of synthetic drugs (Hossain et al., 2014;Urbi and Zainuddin, 2015;. On the contrary, for being comparatively safe, natural products have gained tremendous importance as sources of polypharmacological drugs for infectious diseases, cancers, and neurological disorders Farooq et al., 2021). Moreover, indications of the importance of plants for diverse ailments in religious scripts attracted more researchers focusing on evaluating the scientific validity of traditional claims (Hossain et al., 2014;Hossain, 2016;. So, finding safer alternatives to systematic chemotherapeutic drugs from natural sources are an important and worthy study. Herbs and spices have been commonly used as condiments to enrich aroma, taste, and colour for thousands of years. Even though they are consumed in small amounts, these herbs and spices contain many bioactive compounds and beneficial health effects. The role of spices and herbs in the inhibition of CRC cells growth has been reported in many recent studies (Zheng et al., 2016;Jaksevicius et al., 2017;Aasim et al., 2018;DeLuca et al., 2018;Khor et al., 2018;Wani and Kumar, 2018;Aiello et al., 2019;Rajasekaran, 2019;Buhrmann et al., 2020;Dandawate et al., 2020;Ganesan et al., 2020;Hallajzadeh et al., 2020;Hu et al., 2020;Malmir et al., 2020;Martínez-Aledo et al., 2020;;Pricci et al., 2020;Badsha et al., 2021;Kammath et al., 2021;Karthika et al., 2021). There is increasing evidence of preventing CRC by consuming fruits and vegetables, while red meat enhances the risk factors (Hallajzadeh et al., 2020). Similarly, dietary fibre was contradictory until recent findings showed that high dietary fibre could prevent cancers, including CRC (DeLuca et al., 2018;Masrul and Nindrea, 2019;O'Keefe, 2019). For example, consumption of one to three tablespoons of ground flaxseeds (FS) per day (8-24 g/day) has been suggested as part of a healthy eating pattern that works as a chemotherapeutic agent against CRC development (DeLuca et al., 2018).
Since many disease conditions, including CRC, commonly treated with culinary herbs and spices in traditional medical systems, are considered self-limiting, their purported benefits need critical evaluation intended for CRC management. This would be a worthy study for the community, particularly clinical practitioners and CRC patients. Therefore, in this study, six commonly used herbs and spices: ginger (Zingiber officinale Roscoe), turmeric (Curcuma longa L.), garlic (Allium sativum L.), fenugreek (Trigonella foenum-graecum L.), sesame (Sesamum indicum L.), and flaxseed (Linum usitatissimum L.) were chosen to evaluate their chemoprotective chemotherapeutic roles in CRC management critically and explored the possibility of developing these agents as anti-CRC pharmaceuticals. Scientific evaluation of these plants against cancers, particularly CRC, is increased over the last few years, and turmeric is the most extensively used spice evaluated for CRC ( Figure 1).
Initially, this study comprehensively discussed the molecular basis of CRC development, followed by culinary and traditional uses, current scientific research, and publications of selected herbs and spices on cancers and their role in CRC management with underlying molecular mechanisms of action. Lead compounds have been discussed comprehensively for each herb and spice, including anti-CRC phytoconstituents, antioxidant activities, anti-inflammatory properties, and finally, anti-CRC effects with treatment mechanisms. Future possible works have been suggested where applicable.

MOLECULAR BASIS OF COLORECTAL CANCER
Cancer is a genetic illness caused by oncogene activation, tumour suppressor gene dysfunction, or environmental mutagenesis (Imran et al., 2017). The effective control of cancer solely lies in a better understanding of its pathophysiology, and significant progress has been achieved in comprehending the molecular basis of cancer. Genetic and epigenetic changes play a role in the onset of neoplastic transformation of the healthy epithelium into malignant phases (Gorga, 1998). Progression of CRC is mainly involved with the silencing of tumour suppressor genes and activation of an oncogene (Malki et al., 2020).
As mentioned earlier, both genetic and epigenetic changes in the key genes are responsible for CRC development. This alteration is involved with three major pathways: CIN, MSI, and CIMP pathways (Pino and Chung, 2010). The CIN route is responsible for most CRC cases. This pathway is characterized by widespread abnormalities in chromosomal number (aneuploidy) and loss of heterozygosity. It can be caused by errors in chromosome segregation, telomere stability, or the DNA damage response, though the genes involved are currently unknown (Pino and Chung, 2010). Fearon and Vogelstein described the first multistep genetic model of colorectal tumorigenesis in 1990 (Fearon and Vogelstein, 1990). Later in 2010, Pino and Chung (Pino and Chung, 2010) critically evaluated the CIN pathway of CRC and discussed the role of each gene involved with CRC progression. According to the model proposed, the formation of aberrant crypt foci (ACF) is the initial step of CRC progression. Inactivating the adenomatous polyposis coli (APC) tumour suppression gene through the mutations can activate the Wnt signalling pathway at this stage. Subsequently, activating mutations in the proto-oncogene KRAS, mutations in the tumour suppressor gene TP53, as well as loss of heterozygosity at chromosome 18q are required for progression to larger adenomas and early carcinomas. In a tiny fraction of colorectal tumours, mutational activation of the PIK3CA gene occurs late in the adenoma-carcinoma sequence. Consistent with the evolution of adenomas that are not malignant, CIN is detected in benign adenomas and increases in tandem with tumour progression (Figure 2).
Nuclear Factor-kappa B (NF-κB) is a ubiquitous transcription factor regulating gene expression of inflammatory and immunological cytokines, cytokine receptors, and adhesion molecules in various cell signalling pathways. NF-κB activation also affects the control of apoptotic pathways, cell proliferation, differentiation, migration, angiogenesis, and tumour cell resistance to chemo/radiotherapy (Soleimani et al., 2020). NF-κB binds to an inhibitor, I-kappa B (IκB), present in the cytoplasm of most the quiescent cells and inactivates NF-κB by covering the nuclear localization sequence, blocking DNA binding and nuclear uptake of NF-κB (Baeuerle and Henkel, 1994). However, extracellular stimuli such as oncogenic molecules, and chemo/radiotherapy, cell surface receptors, including tumour necrosis factor receptors, interact with their FIGURE 1 | Scientific evaluation of culinary spices and herbs for the different research, including cancers and colorectal cancer. The value top on the bar represents the per cent (%) value of the total publications of each plant. The data were retrieved from the Scopus database on 15 August 2021 using the search keywords: Ginger OR Zingiber officinale Roscoe, Turmeric OR Curcuma longa L., Garlic OR Allium sativum L., Fenugreek OR Trigonella foenum-graecum L., Sesame OR Sesamum indicum L., Flaxseed OR Linum usitatissimum L., Cancer*, "Colorectal cancer" OR "Colon cancer". CRC: Colorectal cancer. specific ligands to cause an upregulation of the IκB kinase complex, which triggers down-stream genes expression that potentially promotes inflammation and cancer initiation/ progression (Soleimani et al., 2020). In addition, active NF-κB in tumours with wild type Kirsten Rat Sarcoma Virus (KRAS) and KRAS mutations increased the activity of NF-κB signalling in patients with KRAS mutations, and patients exhibited a lower survival and weaker response to first-line treatment compared to other cases (Lin et al., 2012a;Lin et al., 2012b). Therefore, the NF-κB signalling pathway plays a vital role in accelerating cell proliferation, cell survival, and inhibition of apoptosis.
The well-established molecular basis of cancer helps determine confirmatory biomarkers that can improve clinical outcomes in patients with CRC and increase the survival of patients with metastatic cancer. Chemopreventive or chemotherapeutic agents target those biomarkers for the best outcomes to control CRC. In other words, identified biomarkers, such as KRAS and TP53 genes, can be targeted to prevent or control CRC as inhibition of the KRAS gene or activation of the TP53 gene modulate the normal function of cells; thus, cancerous cells cannot sustain growth. Additionally, inhibition of the NF-κB signalling cascade limits cell proliferation; therefore, targeting this cascade may lead to preventive measures, and novel treatment approaches against CRC.
In our current review, we have annexed six culinary herbs that have strong vigour to inhibit the adenomas cell, carcinomas cell, and even several cancerous cell lines such as colorectal cancer, breast cancer, and prostate cancer (Matsuura et al., 2006). Ginger and its components may operate as chemopreventive agents by lowering COX-2 expression, according to in vitro and animal studies (Kim et al., 2005;Citronberg et al., 2013) (Kim et al., 2005;Citronberg et al., 2013). Gingerol works by activating key cell-signalling regulators and pathways such as Bax/Bcl2, p38/MAPK, Nrf2, p65/NF-B, TNF-, ERK1/2, SAPK/JNK, ROS/NF-B/COX-2, caspases-3, -9, and p53 (Wee et al., 2015;de Lima et al., 2018). Turmeric extract suppresses metastasis by regulating several targets, including molecules involved in the Wnt and Src pathways, EMT, and EGFR-related pathways. It also restricts FAK/Src, STAT3, Erk, and Akt pathways suppressing cell proliferation, motility, and migration Li et al., 2021). Garlic and its constituents suppress tumour biomarker aberrant crypt foci (ACF), NF-κB, anti-apoptotic genes (Bcl-2, cIAP1/2, and XIAP), and inflammatory genes (iNOS and COX-2), and EGFR, whereas it induces apoptotic gene expression (Ban et al., 2007;Ngo et al., 2007;Saud et al., 2016;Mondal et al., 2022). A few studies found a significant reduction of ACF with 1% fenugreek or 0.1% or 0.05% diosgenin, which is also implicated in the suppression of COX-2 as well as the stimulation of nuclear factor-B, p53, and p21 expression (Moalic et al., 2001;Raju et al., 2004). Sesamol (100 µM) inhibits the expression of COX-2 and cytosolic prostaglandin E2 synthase mRNA in polyp sections and targets the p53, MAPK, JNK, PI3K/AKT, TNFα, NF-κB, PPARγ, caspase-3, Nrf2, eNOS, and LOX signalling pathways (Shimizu et al., 2014;Majdalawieh and Mansour, 2019). Flaxseed meal elevates the mitochondrial apoptosis genes such as p53 and cyclin-dependent kinase inhibitor 1A (p21) as well as cell cycle arrest genes (Hernández-Salazar et al., 2013). Furthermore, the COX-1 and COX-2 protein level in the colonic tissue is considerably reduced (Bommareddy et al., 2006). well as after chemotherapy and radiotherapy in cancer treatment. Over the past few decades, researchers have realized that ROS plays a significant role in the aetiology of various diseases, including cancer, cardiovascular disease, and inflammation injury. Excessive production of ROS in cellular life needs to be regulated tightly. Because ROS have the potential to initiate the degenerative process in cells; however, living organisms have several antioxidant systems that scavenge the adverse effects of ROS on cells (Karker et al., 2016). These drastic impacts on cells include oxidative stress, damaging biomolecules, including DNA, lipid oxidation, protein degradation, and cellular apoptosis ( Figure 3) (Valko et al., 2007).
ROS are by-products of regular cellular metabolism that play crucial roles in activating signalling pathways in cellular life (Perillo et al., 2020). When cells or tissues are exposed to prolonged environmental stress, ROS are created over an extended period, resulting in irreversible damage to cell structure and function, as well as the induction of somatic mutations and neoplastic transformation (Khandrika et al., 2009). Indeed, oxidative stress is associated with cancer onset and development, either by increasing DNA mutations or generating DNA damage, genome instability, and cell proliferation ( Figure 3) (Fang et al., 2009;Visconti and Grieco, 2009). Additionally, proteins and lipids are also key oxidative targets, and altering these molecules increases the risk of mutagenesis (Schraufstätter et al., 1988). The adverse effects of ROS can be tightly controlled through a sophisticated enzymatic antioxidant system [e.g., superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase, and catalase] (Soraya and Mozafar, 2018).
Chronic inflammation is caused by various biological, pharmacological, and physical factors, and it has been linked to an elevated risk of numerous types of cancer in humans, including CRC. Epidemiological and experimental evidence suggests that oncological illnesses like cancer have been linked to this inflammation (Reuter et al., 2010). This inflammation is now regarded as a "secret killer" for diseases such as cancer. For example, inflammatory bowel diseases such as Crohn's disease and ulcerative colitis are associated with an increased risk of colon adenocarcinoma, and chronic pancreatitis is related to an increased rate of pancreatic cancer (Reuter et al., 2010).
An elevated ROS is produced in the inflammatory cells due to increased oxygen absorption in the damaged area. As a result of the increased ROS, the latent TGF-complex is activated, which binds to its receptor and activates different signalling pathways, such as SMAD2/3, PI3K, MAPK/AP-1, and JNK. (Coussens and Werb, 2002). In addition, inflammatory cells also generate soluble mediators, such as cytokines and chemokines, which persuade FIGURE 3 | Schematic mechanism of oxidative stress and inflammation-induced cancer development. Damaged cells or tissues produce ROS resulting in oxidative stress and/or inflammation. Oxidative stress: regenerated ROS can be detoxified with the presence of balanced detoxifying agents, such as antioxidants. However, excessive ROS induces apoptotic signalling pathways and promotes carcinogenesis in cells with faulty signalling by deregulating biomolecules. Hence, it targets Nrf2 and its regulator Keap1 and downregulates antioxidant enzymes that result in high intracellular ROS levels, which induce cell proliferation, metastasis, and chemoresistance by rescuing Nrf2 transcription. Inflammation: various diseases and stress conditions causes inflammatory cell infiltration that induces ROS and different cytokines. The elevated ROS activates latent TGF-complex, which binds to its receptor and activates signalling pathways such SMAD2/3, PI3K, and JNK. It also activated tyrosine kinase that allowed NF-κB (active form) to enter the nucleus, further activating target genes for chemokines, cytokines, adhesion molecules, and receptors to cause cell proliferation, growth, and differentiation. Akt, protein kinase B; Erk, extracellular signal-regulated kinase; IL, interleukin; JNK, c-Jun N-terminal kinase; Keap1, kelch-like ECH (enoyl-CoA hydratase)-associated protein 1; MAPK, mitogen-activated protein kinase; Nrf2, nuclear-related factor 2; NF-κB, nuclear factor-kappa B; Pi3K, Pi3 kinase; ROS, reactive oxygen species; STAT3, signal transducer and activator of transcription 3; SUZ12, suppressor of zeste 12; TGF, transforming growth factor; TNF, tumour necrosis factor.

THERAPEUTIC POTENTIAL OF CULINARY HERB AND SPICE FOR COLORECTAL CANCER MANAGEMENT
Food is consumed either raw or cooked to provide energy and nutritional support for an organism. In addition to enhancing taste, aroma, and colour, herbs and spices also provide nutritional value. Apart from their culinary uses, ginger, turmeric, garlic, fenugreek, sesame, and flaxseeds are traditionally used for different ailments, including cancers ( Table 1).
These plants are widely investigated for the scientific validity of health benefits or traditional uses, particularly their anti-cancerous role. The extracts or compounds that possess antioxidants showed potential anti-cancerous effects. Antioxidants are substances that, when present in low concentrations compared to the substrate, prevent or delay the oxidation of the substrate. On the other hand, the substrate would otherwise be oxidized by the pro-oxidants. Different parts, plant extracts, and isolated compounds of the selected herbs and spices have potential antioxidant properties that show anti-inflammatory and anti-cancer effects. An overview of their chemopreventive or chemotherapeutic role in CRC management by targeting diverse mechanisms of action is shown in Figure 4.

Ginger
The botanical name of ginger is Zingiber officinale Roscoe, which belongs to the family Zingiberaceae. It is a herbaceous perennial flowering plant that originated in Southeast Asia. It is one of the most consumed dietary condiments globally and is now produced worldwide, including in Bangladesh, India, China, Nigeria, Nepal, Indonesia, and Japan (Surh, 1999). The rhizome, the horizontal stem from which the roots grow, is the central portion of ginger that is widely used and consumed in numerous forms, such as fresh, dried, pickled, preserved, crystallized, candied, powdered or ground (Bode and Dong, 2011).
Ginger is an excellent source of antioxidants used to treat ailments from colds to cancer (Bode and Dong, 2011). The popularity of ginger for scientific research has surged in recent years. As of 15 August 2021 (Scopus database), approximately 12,092 papers with a focus on the beneficial effects of ginger have been published between 1853 and 2021. The papers focused on only cancer is 33%, while 7% focused mainly on CRC (Figure 1). This plant has many other health benefits related to cancers ( Figure 5).

Lead Compounds of Ginger
Ginger has at least 115 compounds (volatile and non-volatile) in fresh and dried rhizomes identified in different extracts. Among these, gingerols, parasols, shogaols, and quercetin are the most common constituents and exert various powerful therapeutic and preventive effects (Bode and Dong, 2011). Examples of volatile components are hydrocarbons, zingiberene, sequiphellandrene, α-curcumin, and other sesquiterpenes, while non-volatile   Table 2) (Fu et al., 2014;Park et al., 2014;Radhakrishnan et al., 2014).

Antioxidant Activity of Ginger
Ginger extracts, powder, and constituents have shown potential antioxidant activity in vitro and in vivo models (Kikuzaki and Nakatani, 1993;Stoilova et al., 2007;Wang et al., 2018;Tanweer et al., 2020;Naliato et al., 2021). These studies showed that solvent has significant effects on the effectiveness of antioxidant  properties. Aqueous ethanolic solution (0.02%) showed high antioxidant activity (Kikuzaki and Nakatani, 1993). The solution was prepared from different extracts of ginger like dichloromethane, methanol, and α-tocopherol. The dichloromethane extract exhibited higher activity than αtocopherol and methanol extract. The ginger extract inhibited the hydroxyl radicals 79.6% at 37°C and 74.8% at 80°C, which showed higher antioxidant activity than quercetin and chelated Fe 3+ in the solution (Stoilova et al., 2007). Gingerol related compounds substituted with an alkyl group bearing 10-, 12-or 14-carbon chain length might contribute to both radical scavenging effect and inhibitory effect of autoxidation of oils; however, there was no significant difference in the activity among the compounds with different alkyl chain length (Masuda et al., 2004). These results suggested that the antioxidant action may be attributed to radical scavenging and substrate affinity. Ginger bioactive compounds can also stimulate a plethora of enzymes, such as glutathione reductase, glutathione S-transferase, and glutathione peroxidase, that help mitigate free radicals that induce oxidative stress startlingly suppress colon carcinogenesis (Manju and Nalini, 2005). Consumption of ginger extracts may reduce or delay the progression of diseases that oxidative stress occurs due to a lack of antioxidant supplementation (Tohma et al., 2017) because ginger cakes or bread showed high antioxidants activity by scavenging peroxyl radicals (Martinez-Villaluenga et al., 2009;Balestra et al., 2011;Ademosun et al., 2021). Therefore, it can assume that gingerbased bakeries or beverages would be effective functional dietary products in managing and preventing cancers.

Anti-Inflammatory Effects of Ginger
Phytocompounds isolated from ginger, such as gingerol and shogaol, can suppress the synthesis of pro-inflammatory cytokines such as IL-1, IL-8, and TNF-α. (Tjendraputra et al., 2001). An NF-κB signalling pathway is linked with chronic inflammatory diseases like cancer, allergy, myocardial infarction, asthma, arthritis, multiple sclerosis, and atherosclerosis. Habib et al. (2008) demonstrated that the ginger extract has the magnificent potential to lessen the expression of the NF-κB signalling pathway. Cyclooxygenases (i.e., COX-1, COX-2) enhance prostaglandin-mediated inflammation. Gingerol impedes COX-2 expression induced by lipopolysaccharides (LPS) (Lantz et al., 2007). A double-blind, placebo-controlled, randomized experiment reported that daily consumption of raw and heat-treated ginger (2 g) for 11 consecutive days resulted in moderate-to-large reductions in muscle pain compared to the placebo (Black et al., 2010). In LPS induced inflammation, one of the lead compounds of ginger, [6]-shogaol reduced the levels of nitric oxide synthases (iNOS), COX-2, and phospho-NF-kB, suppressed histone deacetylase-1 (HDAC-1) expression, and increased histone H3 acetylation expression. [6]-Shogaol can inhibit HDAC-1 expression, comparable to that of commonly used HDAC inhibitors Trichostatin A and MS275 (Shim et al., 2011). This result indicates that a ginger supplement rich with [6]-shogaol could significantly attenuate various inflammatory responses.

Anti-Colorectal Cancer Effects and Mechanisms of Actions of Ginger
Ginger leaves extract induced apoptosis in human colorectal cancer cells, HCT116, SW480 (human colon adenocarcinoma cells), and LoVo by activating transcription factor 3 (ATF3). ATF3 is responsible for the induction of apoptosis in CRC cells by regulating the ERK1/2 pathway, where ginger leaves (50, 100, and 200 μg/ml for 24 and 48 h) interact with the cAMP-responsive element-binding (CREB) site and activate ATF3 (Tang et al., 2002;Hsu et al., 2005;Park et al., 2014). Another investigation reported that ginger extract inhibited CRC cell growth (HCT-116) by down-regulating the K-ras and MMP-2 marker gene expressions. K-ras is crucial in colorectal metastasis by regulating VGEF, protease expression, apoptosis, adhesion, and motility (Lavrado et al., 2015).

Turmeric
Turmeric (Curcuma longa L.) is also derived from the Zingiberaceae family. In addition to improving taste, turmeric was one of the spices used to preserve food. Yellow turmeric rhizomes give an aromatic flavor and slightly bitter taste. (Dhakal et al., 2019). Turmeric rhizomes are an excellent antioxidant source, and it has free-radical scavenging properties (Restrepo-Osorio et al., 2020). Its extracts (1-2%) are considered a natural preservative and free from microbial contamination at least for 90 days of storage (Gul and Bakht, 2015). Turmeric is generally given at a dose of 5-500 mg/kg for nutritional purposes depending on the food categories like dairy products, beverages, cereals, mustard, food concentrates, pickles, sausages, confectionery, and ice cream, meat, fish, eggs, and other confectionaries. It is also mixed with other compounds, including annatto, seasonal sauces, mayonnaise, and butter (Sharifi-Rad et al., 2020). Turmeric is rich in polyphenols and universally known as the "wonder drug of life." The lead compound, curcumin, is responsible for a wide range of pharmacological activities, including antioxidant, anti-cancer, anti-arthritic, anti-microbial, anti-diabetic, anti-inflammatory activities, and avails in the treatment of many ailments, including tendinitis, liver cirrhosis, Alzheimer's disease, heart attack, hypoglycemia, gastrointestinal problems, worms, swelling, cancer, skin and ocular perceiver infections (Gera et al., 2017). Currently, the major focus has been given by scientists on cancer. As of 15 August 2021 (Scopus database), the effect of turmeric/ curcumin on cancer; between 1881 and 2021, was the topic of 11,519 papers, with 53% related to cancer and 16% associated exclusively on CRC (Figure 1). The wide application of curcumin in diverse fields had caused its global market to expand exponentially. The pharmaceutical industry, particularly those focused on anti-cancer medication formulations, is the most significant application category, accounting for more than half of the global market, followed by the food and cosmetic industries (Sharifi-Rad et al., 2020). 3.5% minerals, and other elements (15.67%). Curcumin and calebin A are lead compounds ( Figure 7) with a magnificent biological role in CRC patient management ( Figure 4 and Table 2).

Antioxidant Activity of Turmeric
Turmeric can mitigate the rise of free radical formation in the living cells responsible for damaging the biomolecules, such as lipid, protein, and DNA (Goud et al., 1993). A study reported by Tilak et al. (2004) showed that turmeric, as used in cooking and in-home remedies, and its major compounds have significant antioxidant abilities at different levels of action. This study prepared six different types of standardized aqueous and ethanol extracts using the processed powder or raw turmeric rhizome as per the cooking mood. The ethanol contains more phenolic and flavonoid content than aqueous extracts. In all antioxidant tests using raw and processed turmeric, ethanol extracts were performed over the aqueous extracts. Boiled ethanol extract (10 min) had the strongest activity in two chemical assays -ferric reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picryl hydroxyl (DPPH) radical scavenging test. However, in the ferryl myoglobin assay, ethanol extracts (raw turmeric stirring in ethanol for 1 h) exhibited the highest total antioxidant activity (TAA). Boiling the aqueous extracts increased their potency compared to the aqueous extracts. Turmeric boiling extracts were more efficient at scavenging 2,2-azobis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) radicals than aqueous turmeric extracts. There is no doubt numerous studies reported on the antioxidant activity of turmeric extracts and their different isolated compounds. At the same time, the in vitro antioxidant activities of turmeric extracts have been supported by the in vivo studies to support its pharmacological applications (Sreekanth et al., 2003;Dall'Acqua et al., 2016;Mohammed et al., 2020). A proprietory formulation containing extract of turmeric obtained by supercritical carbon dioxide gas extraction and post-supercritical hydroethanolic extraction is known as Smoke Shield. Administration of Smoke Shield to mice increased antioxidant enzymes in blood, liver, and kidney (Sreekanth et al., 2003). Smoke Shield increased glutathione-S-transferase activities in the liver and kidney. Additionally, it increases superoxide dismutase and glutathione, whereas it decreases glutathione peroxidase in smokers' blood. Smoke Shield contains significant antioxidant action, inhibits phase I enzymes, and increases detoxification enzymes, making it a chemoprotective herbal preparation (Sreekanth et al., 2003). The oral administration of turmeric extract to healthy rats decreased urinary levels of allantoin, m-tyrosine, 8-hydroxy-2′-deoxyguanosine, and nitrotyrosine. This finding supports the in vivo antioxidant effect of turmeric (Dall'Acqua et al., 2016). Another recent in vivo antioxidant study of methanol extract of turmeric showed a significant decrease in SOD, catalase (CAT) and GPx levels in both liver and kidney of Alloxan-induced diabetic rats (Mohammed et al., 2020). These findings suggested that turmeric supplements could potentially neutralize the ROS level in cells even if used in cooking, either stirring on oil for 10 min or 30 min in aqueous; however, further investigation on the complex role of antioxidant curcumin effects is required before making a precise conclusion.
The main bioactive compound of turmeric, curcumin (42 µM) integrated with rat liver mitochondria, reduces ascorbate-Fe 2+ driven lipid peroxidation significantly. During incubation (0-60 min), the per cent inhibition was almost 100% without any lag period of inhibition (Tilak et al., 2004). Another phytoconstituent of turmeric called turmeric was an effective antioxidant/DNA protectant/antimutagen. It has three methionine residues that are responsible for its antioxidant properties. Turmeric at a 183 nM is highly protective (80%) to membranes and DNA against oxidative injury. Additionally, it is noncytotoxic up to milligrams doses in human lymphocytes (Srinivas et al., 1992). Curcumin and turmeric controlled oxidative stress by reducing the level of thiobarbituric acidreactive substances (TBARS) and protein carbonyls and repealing altered antioxidant enzyme activities in rat models (Suryanarayana et al., 2007). Many other studies also reported that turmeric extracts and their constituents have potential free radical scavenging activity, and ethanol extracts are more efficient than aqueous extracts (Cousins et al., 2007;Singh et al., 2010;Lim et al., 2011;Tanvir et al., 2017;Arumai Selvan et al., 2018). The formulation of turmeric extracts using modern technology like spray-dried microparticles (Martins et al., 2013), silver nanoparticles (Arumai Selvan et al., 2018), and puffing (Choi et al., 2019) enhance the antioxidant activity of turmeric.

Anti-Inflammatory Effect of Turmeric
Traditionally, as an anti-inflammatory antidote in ayurvedic medicine, Turmeric powder is implicated as an antiinflammatory antidote. In a rat model, the production of these enzymes was elevated by curcumin treatment (Tvrdá et al., 2016). In the in-vitro experiment, the macrophage-mediated inflammation due to ROS production has reduced by giving 10 μM curcumin (Amano et al., 2015). The increasing detrimental bacterial population in the colon so prompts to produce of carcinogenic chemicals, toxins that are responsible for the development of colon cancer; for instance, Bacteroides fragilis produces Bacteroides fragilis toxins (BFTs) that subsequently activate the STAT3 signalling pathway and stimulate IL-17 cytokines production that subsequently promotes NF-κB and Wnt signalling pathway activation leading to abnormal cell division (Chung et al., 2018). Caleb in A is a potent anti-inflammatory component of turmeric responsible for inhibiting cancer formation through this NF-κB signalling pathway (Buhrmann et al., 2020). Another investigation has demonstrated that the inflammation mediated by NF-κB activation is suppressed by averting IκBα kinase and AKT signalling pathway because of using curcumin (Aggarwal et al., 2006). The administration of curcumin is also thought to have reduced the expression of inflammatory cytokines, such as C-reactive protein, cyclooxygenase-2 (COX-2), TNF-, CXCR-4, MIP-1, IL-1, IL-6, and IL-8 (Gonzales and Orlando, 2008;Wang and Dubois, 2010;Kim et al., 2012;Afzali et al., 2021).

Anti-Colorectal Cancer Effects and Mechanisms of Actions of Turmeric
Calebin A suppressed the expression of Nuclear Factor-kappa B (NF-κB), which promotes the anti-apoptotic B cell lymphoma extralarge (BCL-xL), B-cell lymphoma (BCL-2), surviving, proliferation (Cyclin D1), invasion (MMP-9), metastasis (CXCR4) biomarkers, as well as down-regulated apoptosis (Caspase-3) gene biomarkers, ultimately leading to apoptosis in human colorectal adenocarcinoma (HCT116) cells (Buhrmann et al., 2020). Rajitha et al. (Rajitha et al. (2016) demonstrated that the administration of 25 µM curcumin, a potential NF-κB inhibitor, significantly suppressed NF-κB activation via inhibiting the transcription factor E2F-1 and thymidylate synthase as compared to untreated cell lines. This treatment resulted in cell cycle arrest at the G0/G1 phase with a concomitant decrease in the number of cells in the S, and tumour growth was significantly reduced in the CRC cell lines HCT116 and HT-29. The western blotting analysis further revealed that curcumin significantly decreased the levels of cyclin D1, CDK4, and pRb and increased p16 and p21 in both cell lines compared to controls ( Figure 8) (Rajitha et al., 2016). It has also been shown to emerge with anti-inflammatory and anti-tumour properties by the induction of apoptosis and modulating different signalling pathways, such as mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), p38, Jun N-terminal kinase (JNK) in gastric cancer, and neurofibroma (Li et al., 2008;Lee et al., 2019). Curcumin and its analogues have been an effective chemotherapeutic agent and chemosensitizer by regulating specific microRNAs, signalling pathways, and epithelialmesenchymal transition (Cai et al., 2018).

Garlic
Another commonly consumed spice is garlic (Allium sativum L.), a member of the family Liliaceae (Shang et al., 2019). Garlic can be consumed raw or cooked and in powder or oil form. Garlic as traditional medicine has been documented in ancient writings of Egypt, Greece, China, and India as early as 3,000 years ago (Rivlin, 2001;Omar and Al-Wabel, 2010). Garlic has been shown to reduce the incidence of heart disease and cancer in epidemiologic and preclinical investigations, and it has also been claimed to be an anti-cancer dietary component (Bayan et al., 2014). There are around 33 sulfur compounds, including alliin, allicin, ajoene, allyl propyl disulfide, diallyl trisulfide, S-allyl cysteine, vinyldithiines, S-allyl mercapto cysteine, and others, several enzymes (i.e., allinase, peroxidases, myrosinase), 17 amino acids like arginine and others, and minerals, such as selenium, germanium, tellurium and other trace minerals (Newall et al., 1996;Martins et al., 2016;Abe et al., 2020). As of 15 August 2021 (Scopus database), 19,339 papers related to the merits of garlic consumption have been documented between 1854 and 2021. One-third of these published records were related to its benefits in cancer modulation, while 8 % pivoted on its benefits for CRC prevention and management ( Figure 1). There is compelling evidence that garlic and related sulfur components can reduce cancer risk and affect the biological behaviour of tumours. A high intake of garlic is associated with decreased risks for stomach and CRC (Omar and Al-Wabel, 2010).

Lead Compounds of Garlic
Garlic's pungent flavour renders it a daily seasoning or condiment in Asian cuisine. Prominent medicinal values and uses of garlic have been seen since ancient times. Garlic has more than 200 chemicals. The leading bioactive molecules among these compounds are diallyl sulfide, diallyl disulfide, diallyl trisulfide, diallyl tetrasulfide, S-allyl mercaptocysteine, allicin, selenomethionine, and se-methyl-Lselenocysteine ( Figure 9) (Czepukojc et al., 2014). The potential chemotherapeutic activities of the aforementioned compounds in colorectal cell lines are listed in Figure 4 and Table 2.

Anti-Colorectal Cancer Effects and Mechanisms of Actions of Garlic
Aged garlic extract (AGE) and its bioactive compounds are good chemopreventive agents for CRC because of their antiproliferative action on colorectal carcinoma cells and inhibitory activity on angiogenesis. AGE suppressed the proliferation of different CRC cell lines, namely DLD1, COLO205, HT29, SW480, and SW620 (Matsuura et al., 2006;Jikihara et al., 2015;Tung et al., 2015). It had diverse impacts on the invasive activities of these cell lines, and AGE showed a significant reduction in invasive activity on SW480 and SW620 cells; however, it did not affect the invasive activity of HT29 cells (Matsuura et al., 2006). There appears to be a relationship between the effect of AGE and the type of cancer cells being treated. AGE improved the endothelial cells' adherence to collagen and fibronectin, whereas its bioactive compounds reduced cell motility and invasion. In addition, AGE had a strong inhibitory effect on the proliferation and tube formation of endothelial cells (Matsuura et al., 2006). SW620 is a metastasized SW480, and both cell lines have been documented to have increased p53 levels, while HT-29 cells consist of mutated p53 (Eng et al., 2021). Thus, it is plausible that the bioactive compounds interact with the molecules such as p53 that ensure cell cycle checkpoints are conducted rigorously. AGE decreased the number of ACF but did not affect gross tumour pathology in the DLD1 human CRC cell line. AGE inhibited the proliferation of adenoma and adenocarcinoma lesions but did not affect normal colon mucosa. It delayed cell cycle progression by inhibiting cyclin B1 and Cyclin-dependent kinase 1 (cdk1) expression but did not trigger apoptosis in DLD1 (Jikihara et al., 2015). Bioactive compounds of garlic, particularly selenomethionine and se-methyl-L-selenocysteine, decreased ACF and induced apoptosis by about 80% by activating caspase 3. In addition, AGE delayed cell cycle progression by inactivation of NF-κB signalling and downregulation of cyclin B1 and cdk1 expression during the G2/M-phase ( Figure 8) (Jikihara et al., 2015;Tung et al., 2015). Se-methyl-L-selenocysteine increased Fas and FasL expression, followed by the caspase-3, caspase-8, DNA fragmentation factor, and poly(ADP-ribose) polymerase cleavage. Se-methyl-L-selenocysteine also increased Bax protein levels while decreasing Bid and BCL-2 protein levels. However, this compound caused apoptosis via endoplasmic reticulum stress rather than reactive oxygen species stress. The cleavage of caspase-12 and caspase-9 increases growth arrest and protein levels of GADD 153 and 45. In COLO 205 cells, Semethyl-L-selenocysteine reduced ERK1/2 and PI3K/AKT protein levels while increasing p38 and JNK protein levels (Tung et al., 2015). These results suggested that AGE or garlic's bioactive compounds, mainly selenomethionine and se-methyl-Lselenocysteine, could prevent tumour formation by inhibiting angiogenesis by suppressing endothelial cells motility, proliferation, and tube formation. Therefore, they could be good chemopreventive agents for CRC because of their antiproliferative action on colorectal carcinoma cells and inhibitory activity on angiogenesis.

Fenugreek
Fenugreek (Trigonella foenum-graecum L.) belongs to the family Leguminosae. It has long been used as a spice to improve the sensory quality of cuisines across the world, including in Bangladesh, India, and Pakistan (Wani and Kumar, 2018;Singh et al., 2020). Its seeds and green leaves, commonly used as leafy vegetables and seasonings, are now widely cultivated for medicinal purposes. They also enhance flavour, colour, and texture in foods (Tewari et al., 2020). Although modern medicine has made incredible advances, the usage of herbal plants for treating or preventing diseases is still widely used due to their diverse nutraceutical capabilities and safety. Among many spice crop plants that are nutritious, functional, and therapeutic, fenugreek is popular with all these characteristics. Recently, it has gained tremendous scientific attention for further evaluation and validation of nutraceutical and health benefits, especially lifestyle-related diseases and cancer. Our systematic investigation in the Scopus database revealed that scientists published around 3,713 papers between 1931 and 2021. Almost a quarter of the articles focused on cancers, and 5% of papers precisely focused only on CRC (Figure 1). The health benefits of fenugreek that lead to anti-cancer effects are summarised in Figure 10.

Lead Compounds of Fenugreek
Since antiquity, fenugreek has been a member of the Fabaceae family and has been extensively utilized as Ayurveda in traditional and alternative medicine systems (Aasim et al., 2018;Rajasekaran, 2019). It is rich in several phytochemicals, of which diosgenin (a saponin) ( Figure 11) has anticarcinogenic properties ( Table 2) (Raju et al., 2004).

Anti-Colorectal Cancer Effects and Mechanisms of Actions of Fenugreek
Multiple functional and molecular targets are involved in the anti-cancer effects of fenugreek or its bioactive compounds, such as apoptosis in tumour cell lines, especially in human CRC ( Table 2) (Raju et al., 2004). In 1,2-Dimethylhydrazine-treated mice, a diet rich in fenugreek seed powder reduced colon tumour incidence and lipid peroxidation LPO while simultaneously increasing GPx, glutathione S-transferase (GST), SOD, and catalase activity in the liver (Sushma and Devasena, 2010). Another study demonstrated that diosgenin inhibited the production of azoxymethane (AOM)-induced aberrant crypt foci, a preneoplastic colonic lesion in F344 rats. This compound induced apoptosis in HT-29 human colon cancer cells by suppressing BCL-2 and activating caspase-3 protein expression, implying its potential as a colon cancer preventive agent (Raju et al., 2004).

Sesame
Sesame (Sesamum indicum) from the Pedaliaceae family is one of the earliest domesticated oilseed crops known to humankind with its multifarious uses. It is mainly consumed in various cuisines and preferably used with bread, biscuits, crackers, and so forth and as a seasoning in food worldwide (Namiki, 2007). Sesame has an essential role in human nutrition due to its rich chemical compositions like oil (44-58%), protein (18-25%), carbohydrates (~13.5%), minerals and vitamins (Elleuch et al., 2007;Hassan, 2012;Lim, 2012). Sesame seeds have multiple potential bioactive compounds that are beneficial components in food and are accountable for disease-preventing properties. These chemical compounds include phenolics, carotenoids, phytosterols, and polyunsaturated fatty acids, often utilized as antioxidants and for other purposes (Pathak et al., 2017). Recent studies demonstrated that the leaves and shoots of sesame plants are used as vegetables, and the leaves contain valuable nutrients such as amino acids responsible for various traditional uses, including pain relief, catarrh, eye pain, bruises, and erupted skin lesions. In Japan, young sesame leaves (30-70 cm tall, 40-60 days after planting) are dried and sold as a health food supplement (Fuji et al., 2018).
The seeds contain lignans such as sesamin and sesaminol and are highly valued as traditional health and nutraceutical food. Young sesame leaves contain three iridoids (lamalbid, sesamoside and shanzhiside methyl ester) and seven polyphenols (cistanoside F, chlorogenic acid, pedalitin-6-O-laminaribioside, pedaliin, isoacteoside, pedalitin and martynoside), and acteoside. These compounds show potential radical scavenging effects in assays like the DPPH, ABTS, and superoxide anion radicals test (Matsufuji et al., 2011;Fuji et al., 2018). However, sesamin, a major lignan in sesame oil did not show antioxidant in vitro activity (Nakai et al., 2003). Interestingly, on the other hand, this compound showed protective effects against oxidative damage in rat liver. The same metabolites were found as glucuronic acid and/or sulfuric acid conjugates in substantial amounts in rat bile after oral administration of sesamin (Nakai et al., 2003). Therefore, sesamin is considered as a prodrug. On giving 10 mg/kg or 100 mg/kg of sesamin (S10, S100) to 32 male ddY mice 2 h before swimming exercise using a new forced-swimming apparatus, their plasma lipid peroxide level was significantly suppressed, while the level in the control group increased significantly after exercise (p < 0.01). S100 showed significantly higher total GPx activity and GST activity in the liver compared to control (p < 0.05) (Ikeda et al., 2003). This finding suggested that sesamin may enhance liver LPO degradation, resulting in strong protective effects against exercise-induced plasma lipid peroxidation. Sesamin in vivo metabolites with the catechol group is the most efficient antioxidants (Papadopoulos et al., 2016). The highly antioxidative action of sesame oil has been clarified, and it has been determined that recently discovered lignans mediate with tocopherols. A novel synergistic effect of sesame lignans with tocopherols has been found, and it is believed to be responsible for the antiaging effect of sesame. Sesame lignans inhibit metabolic decomposition of tocopherols, which results in the antiaging effect of sesame being attributed to strong vitamin E activity (Namiki, 2007). A systematic search in the Scopus database showed that around 11,089 articles were published between 1898 and 2021. Among these publications, about 15% emphasized cancers, and 2% precisely concentrated on CRC alone (Figure 1).

Lead Compounds of Sesame
Sesame from the Pedaliaceae family generally refers to sesame seeds. It is one of the oldest condiments and a commercially significant oilseed crop (Queen of oilseed crops) with 40-60% oil and medicinal value due to the presence of a broad spectrum of bioactive molecules, including sesamin, sesamol, sesamolin, and sesaminol ( Figure 12 and Table 2) (Zohary and Hopf, 2000;Aasim et al., 2018).

Anti-Colorectal Cancer Effects and Mechanisms of Actions of Sesame
Sesamol is one of the prominent biomolecules of sesame seeds that confers chemopreventive properties and analgesic effects ( Table 2). It targets p53, MAPK, JNK, PI3K/AKT, TNF, NF-B, PPAR, caspase-3, Nrf2, eNOS, and LOX signalling pathways, suggesting that sesamol possesses potent anti-cancer properties. It has a wide range of biological functions, including inhibition of lipid peroxidation and enhancement of radical scavenging, upregulation of antioxidant enzymes, suppression of TNFα and IL-1β expression, inhibition of NF-κB signalling, suppression of LOX-1 and 5-LOX activity, induction of apoptosis, arresting cell growth at different phases of the cell cycle and modulation of caspase-3, p53, BAX, and BCL-2 expression (Gupta et al., 2009;Chu et al., 2010a;Chu et al., 2010b;Wu et al., 2015;Kim et al., 2021). In HCT116 cells, sesame leaf extract (250 g/ml and 500 g/ml) induced apoptosis and cell cycle arrest during the G2/M phase. This extract increased the G2/M cell population to 2.3-6.6-fold of the control, with a concurrent drop in G0/G1 and S phase cell populations, demonstrating that sesame leaf extract has a G2/M arresting function (Kim et al., 2021).

Flaxseed
Flaxseed (Linum usitatissimum L.) from the Linaceae family is one of the world's oldest cultivated herbaceous crops. It is still  widely grown for its oil, fibre, and nutritional value. Flaxseed oil is high in omega-3 fatty acid linolenic acid (55%), an attribute that boosts its role as a functional food. Additionally, flaxseeds are used in animal feed to boost reproductive health (Oomah, 2001;Turner et al., 2014). The flaxseed products include whole seed (ground), flaxseed oil (partially defatted), fully defatted (solvent extraction), mucilage extract, flaxseed hull, oleosomes, and alcohol extract. Each of these products has particular health benefits. Reports typically neglect the presence of many bioactive chemicals in flaxseed fractions or attribute the impact to a single component. However, whole flaxseed is widely accepted as a healthy food with anti-cancer activity (Shim et al., 2014). In female rat mammary glands, flaxseed flour reduces epithelial cell proliferation and nuclear abnormalities that indicate the reduction of mammary tumour growth in the later stages of carcinogenesis (Serraino and Thompson, 1991;Thompson et al., 1996). Recently the growth of cancer research using flaxseeds has increased significantly. Our team's systematic literature search (Scopus database) revealed that about 7,357 articles were published between 1844 and 2021. About 22% concentrated on cancers among these publications, and 4% was specifically spotlighted on CRC (Figure 1).

Lead Compounds of Flaxseed
Flaxseed is one of the world's oldest crops, grown since the dawn of civilization. Flaxseed treated various ailments in India, Sri Lanka, Greece, Rome, Egypt, and many other countries and enriched the Ayurveda and traditional Chinese medicine system (Goyal et al., 2014). Due to its high fibre level, omega-3 fatty acids, flavonoids, and phytoestrogens, flaxseed usage in reducing human CRC risk are gaining attention (Calviello et al., 2007;Lattimer and Haub, 2010;Kajla et al., 2015). Moreover, flaxseed is one of the most significant plant sources of linolenic acid, an omega-3 polyunsaturated fatty acid (PUFA) (49-60%), which is linked to a lower risk of colonic neoplasms ( Figure 13 and Table 2) (Goyal et al., 2014;DeLuca et al., 2018).  In vitro studies and animal models suggest that diets high in 3-PUFA may protect against malignancies, such as colon cancer, whereas treatment with 6-PUFA may inhibit cancer cells proliferation. For example, mice fed diets enriched in αlinolenic acid, which enhanced plasma levels of α-linolenic acid (ALA) and its metabolites eicosatetraenoic acid (EPA) and docosahexaenoic acid (DHA), showed a reduction in the growth of transplanted colon cancer cells (Danbara et al., 2005;Bommareddy et al., 2010;Chamberland and Moon, 2015). In case-2 human colon adenocarcinoma cells, ALA has been demonstrated to inhibit cell proliferation and induce apoptosis (Bommareddy et al., 2010). SW480 cells treated with enterolignans (enterodiol (ED) alone or in combination with enterolactone (EL)) showed a dosedependent reduction in cell number, induction of S-phase cell cycle arrest, elevated cyclin A protein levels, an increased proportion of apoptotic cells (0-40 mol/L). Similar results were observed in a study using Colo 201 cells treated with EL, where apoptosis was modulated. Cell proliferation was decreased by the up-regulation of an apoptosis-inducing protein (a cleaved form of Caspase-3) and the down-regulation of both an apoptosis-inhibiting protein (BCL-2) and proliferation cell nuclear antigen (PCNA) protein (Danbara et al., 2005). Regulation of transcription in apoptotic genes (BCL-2, CCND1, and c-Myb) and cell cycle regulation were reported using Young Adult Mouse Colonocytes treated with low levels of EL (1 M) and ED (5 M) (DeLuca et al., 2018).

THE WAY FORWARD
Significant ground-breaking knowledge of molecular mechanisms behind CRC development revealed that dietary factors might be associated with CRC development at an increasing rate. However, the evidence to date is regrettably inadequate due to its highly complex mechanisms. Another significant association of intestinal microbiota with CRC has been predicted. Again, intestinal microbiota balance depends on the dietary habits and alterations of balanced intestinal microbiota involved with CRC development and progression (Leeming et al., 2019;Wong and Yu, 2019). However, modulation of the gut microbiota is a promising strategy to enhance treatment efficacy and reduce the adverse effects of CRC therapies (Wong and Yu, 2019). Many challenging issues, including aetiology, diagnosis, treatment, and management, need to be addressed to properly manage CRC and identify the key concerns for a long-term solution.
For appropriate management of CRC, several steps are required to follow for this global issue. Besides early identification and screening of high-risk communities and individuals, taking preventive measurements through consuming high dietary foods and maintaining a normal lifestyle is essential. This study revealed that consuming culinary herbs and spices might help prevent and cure CRC. They showed potential growth inhibition of human colorectal cancer cells by regulating relevant molecular signalling pathways. The bioactive compounds from these herbs and spices can be isolated and purified through several techniques, including convention extraction or green techniques like supercritical or subcritical fluid extraction. Some sophisticated analytical tools can be applied to purify and identify pure compounds, such as the High-Pressure Liquid Chromatography (HPLC) technique, Liquid chromatographymass spectrometry (LC-MS) analysis, LC-MS-mass spectrometry (LC-MS-MS), and Gas chromatography-mass spectrometry (GC-MS) (Hossain et al., 2014;. To develop stable drugs, isolated compounds can be formulated in different drug forms like tablets, suspension or emulsion (Hua, 2019). They also might be incorporated with nanoparticles and encapsulated in the biodegradable polymer for target-specific drug delivery (Begines et al., 2020).
Some additional measurements are highly recommended as follows: 1) public cancer registration for tracking CRC incidence and survival, 2) government should provide quality medical care for timely diagnosis and treatment, 3) ensure better-personalized therapy and easy access to clinical trials for CRC patients, and 4) increased awareness of CRC as well as about other comorbidities to improving cancer care and research for proper management of this global issue.

CONCLUSION
Literature has provided evidence that herbs and spices have potential roles in preventing and reducing CRC severity. All the six common herbs and spices, namely ginger, turmeric, garlic, fenugreek, sesame, and flaxseed, are useful in preventing CRC. Apart from chemotherapeutic uses, these culinary herbs and spices-derived substances could have a salubrious indication for CRC prevention and management. Their mechanisms of action are mainly mediated through BCL-2, K-ras, and MMP pathways, caspase activation, the extrinsic apoptotic pathway, and the regulation of ER-stressinduced apoptosis. Therefore, these herbs and spices are good candidates for chemopreventive agents for CRC due to their antiproliferative action on colorectal carcinoma cells and inhibitory activity on angiogenesis.


s2fieldsofstudy: Biology Medicine

text:
Systemic consequences of abnormal cholesterol handling: Interdependent pathways of inflammation and dyslipidemia

Metabolic conditions such as obesity and associated comorbidities are increasing in prevalence worldwide. In chronically inflamed pathologies, metabolic conditions are linked to early onset cardiovascular disease, which remains the leading cause of death despite decades of research. In recent years, studies focused on the interdependent pathways connecting metabolism and the immune response have highlighted that dysregulated cholesterol trafficking instigates an overactive, systemic inflammatory response, thereby perpetuating early development of cardiovascular disease. In this review, we will discuss the overlapping pathways connecting cholesterol trafficking with innate immunity and present evidence that cholesterol accumulation in the bone marrow may drive systemic inflammation in chronically inflamed pathologies. Lastly, we will review the current therapeutic strategies that target both inflammation and cholesterol transport, and how biologic therapy restores lipoprotein function and mitigates the immune response.

Introduction
Chronic inflammatory conditions have significantly higher rates of cardiometabolic disorders associated with abnormal cholesterol levels and poor cholesterol trafficking. In diseases of cholesterol accumulation, it is becoming evident that cholesterol handling plays a consequential role in driving systemic inflammation and promoting cardiovascular disease (1). Moreover, in chronic inflammatory conditions such as psoriasis, cholesterol accumulation may be the culprit in rampant inflammation, insulin resistance and a heightened risk of cardiovascular disease (2,3). In this review, we summarize the current literature on the interdependent relationships between abnormal cholesterol handling and s y s t e m i c i n fl a m m a t i o n , a n d t h e i r c o n n e c t i o n t o cardiovascular disease.

Abnormal cholesterol transport
It is well known that unfavorable cholesterol profiles contribute to atherosclerosis, leading to life-threatening complications such as stroke, and confers a heightened risk of cardiovascular events and mortality (4)(5)(6). Cholesterol accumulation is often described in reference to the vasculature, however, a reduction in systemic cholesterol transport would result in accumulation throughout the periphery and may overload the intracellular compartments. Evidence of this may be found in studies of dementia that show cholesterol accumulation at mid-age is associated with an elevated risk of cognitive decline (7). Further, Niemann-Pick disease, a condition with impaired intracellular cholesterol transport, displays both cognitive and respiratory impairment, among other inflammatory ailments (8). Removal of excess cholesterol from peripheral tissues for excretion is the primary role of highdensity lipoprotein (HDL), measured as cholesterol efflux capacity (CEC). Over the last decade, clinical trials have focused on increasing HDL quantity in an effort to reduce cardiovascular events. However, minimal improvements were observed and in some cases adverse events were reported (9). HDL function, which can be measured as CEC (10), is now being investigated as both a diagnostic and therapeutic target, to improve cardiovascular event prediction and improve outcomes.

Cholesterol efflux capacity and cardiovascular events
Over the last decade, epidemiological studies have reported elevated risk of cardiovascular disease and events with impaired CEC, suggesting CEC may contribute to atherosclerosis initiation and progression (10,11). CEC has an inverse association with carotid intima-media thickness and the likelihood of angiographic coronary artery disease, independent of HDL cholesterol levels (10). In the JUPITER (Justification for the Use of Statins in Prevention: An Intervention Trial Evaluating Rosuvastatin) trial, CEC independently correlated with cardiovascular events in a cohort of mostly white male participants on intensive statin therapy (12). The PREVEND (Prevention of Renal and Vascular End-stage Disease) cohort determined that CEC predicted cardiovascular events in the general population, independent of apolipoprotein-A1 (ApoA-1) and HDL (13). Moreover, the multiethnic Dallas Heart Study showed when patients without CVD were stratified by CEC quartiles in fully adjusted models, the highest quartile of CEC had a 67% reduction in cardiovascular risk compared to the lowest quartile (1). Further, the study found that while black men and women had significantly higher rates of CVD, no difference in CEC was detected beyond adjustment (14). In the event of a myocardial infarction (MI), CEC may be protective; with increased serum CEC associated with a lower rate of mortality after an MI (15). Interestingly, one study found that heightened CEC with concurrent ApoB depletion increased the risk of MI and stroke over time, suggesting cholesterol elimination below a certain threshold may be detrimental to vascular health (16). Curiously, while women are at a lower risk of CVD, and CEC levels are enhanced by estradiol levels, there is no significant difference in CEC between sexes (17). Taken together, these findings highlight the critical role of CEC in vascular health and suggest that targeting CEC for therapeutic development may prove efficacious in the reduction of cardiovascular events.

Interdependent pathways between cholesterol and immunity
Cholesterol uptake within immune cells and peripheral tissues occurs through the lysosomal compartments by receptor-mediated endocytosis. Cholesterol is hydrolyzed by lipoprotein lipase in the lysosome into free cholesterol and a fatty acid (18). Cholesterol is then shuttled to either the plasma membrane to maintain membrane integrity and homeostasis, or to the endoplasmic reticulum for conversion into hormones, bile salts or efflux out of the cell. Nuclear factor erythroid 2 related factor-1 (NRF1) is a receptor in the endoplasmic reticulum that functions as a cholesterol sensor to maintain intracellular homeostasis (19). In the liver, high intracellular cholesterol load prompts NRF1 to upregulate ATP-binding cassette subfamily A member 1 (ABCA1) expression for cholesterol export out of the cell, requiring optimal HDL function to receive cholesterol. However, failure to remove excess cholesterol leads to intracellular accumulation and the inflammatory response is primed (19). In macrophages, accumulation of cholesterol is tightly linked to atherosclerotic plaque formation in the coronary arteries (20). Removal of cholesterol through efflux to ApoA-1 on HDL is the primary method of cholesterol displacement and this process occurs through ABCA1 or ABCG1 on macrophages that directly interacts with ApoA-1. The interaction of ABCA1 or ABCG1 with HDL is dependent upon HDL size; larger HDL molecules receive cholesterol through ABCG1 compared to ABCA1, which typically delivers cholesterol to smaller HDL molecules (21). Cholesterol efflux through ABCA1 and ABCG1 modulates downstream immunological signaling. In macrophages specifically, efflux through ABCA1 and ABCG1 downregulates toll-like receptor 2, toll-like receptor 3, and toll-like receptor 4 expression, which reduces nuclear factor−kB (NF-kB) expression and thus decreases inflammasome activation (22). Murine studies show that macrophages lacking ABC transporters have heightened tumor necrosis factor-alpha (TNF-a) secretion (22) and excess formation of lipid rafts, further stabilizing inflammatory signaling (23). Further, the removal of excess cholesterol from ABC-deficient macrophages decreases their inflammatory response and reduces lipid-raft formation (22). These findings are not specific to macrophages; atherosclerotic mice lacking ABCA1 have increased circulating neutrophils and more neutrophil extracellular trap (NET)formation, an acute pro-inflammatory release of nuclear DNA (24).
Cholesterol crystals are an emerging area of research that may partially explain the observed relationships between cholesterol accumulation, immune cell activation and atherosclerosis. Cholesterol crystals are highly prevalent features in lipid-rich necrotic core, a high-risk coronary plaque feature found in late atherosclerosis (25). The formation of cholesterol crystals is thought to relate to a dysfunction in cholesterol transport, and the size and composition of these crystals are hypothesized to contribute to plaque rupture (25). Cholesterol crystals are known to activate the NOD-like receptor protein 3 (NLRP3) inflammasome in myeloid cells, perpetuating systemic inflammation (26) Cholesterol crystals expedite neutrophil extracellular trap (NET) formation, leading to Thelper (H)-17 cell recruitment (27). In addition, cholesterol crystals can accumulate in the lysosomes of monocytes and neutrophils, leading to lysosomal destabilization and downstream activation of NLRP3 inflammasomes (28). Taken together, this indicates that cholesterol accumulation causes a shift towards an inflammatory phenotype in myeloid cells, modulating the immune response.
The observed in vivo relationships in preclinical models can be translated to clinical models. Patients with ABCA1 mutations have reduced CEC and HDL concomitant with increased amounts of TNF-a and interleukin (IL)-6. Positron emission tomography (PET) scans of these patients further revealed increased fluorodeoxyglucose (FDG)-measured inflammation of the aortic arch when compared to controls (29). Similarly, Tangier disease, an inherited disease caused by a loss offunction mutation in the ABCA1 gene, associates with low HDL levels, decreased CEC and increased serum IL-1b and IL-18, pro-inflammatory cytokines released upon inflammasome activation (24). Indeed, these findings confirm the intricate relationship between dyslipidemia and systemic inflammation and suggest a role of CEC as a mediator between the two pathologies ( Figure 1).

Cholesterol and the bone marrow
Poor cholesterol trafficking and an overactive immune system are both prominent in cardiovascular disease and autoimmunity, with monocytes and neutrophils representing critical drivers (13). The linkage between dyslipidemia and innate immunity has been studied extensively in mice and translated to humans (30). In lowdensity lipoprotein (LDL)-receptor knockout mice, haploinsufficiency of ApoA-1 reduces HDL and ApoA-1, leading to the expansion of hemopoietic stem and progenitor cells (HSPC) into monocytes in the bone marrow (31). Further, deficiency in ABCA1 leads to cholesterol accumulation concomitant with hyperproliferation of monocytes and neutrophils, which is exacerbated by a high-fat diet (32). In humans, bone marrow derived HSPCs from patients with hypercholesteremia showed a migratory gene profile, indicating these cells were poised to exit the bone marrow (25), and their transcriptome was skewed towards monocyte proliferation (33). Familial hypercholesteremia (FH) patients have similar immune profiles; the circulating monocyte populations were continuously active in a state of trained immunity (34), which persisted despite treatment with lipid-lowering therapy that rectified high LDL cholesterol. This highlights that the residual inflammatory risk may be undeterred by reducing circulating cholesterol levels once the inflammatory response has been programmed. Additionally, LDL cholesterol from patients with FH associated with circulating monocyte populations and had an inverse relationship between monocytes and HDL (35). Moreover, in hyperlipidemic children, LDL cholesterol associated with monocytes (33). In pathologies of chronic inflammation with poor CEC, imaging studies showed that bone marrow activation assessed by PET-computed tomography (CT) associated with coronary artery disease, high-risk coronary plaque features, and monocyte and neutrophil populations (36). It is becoming evident that in humans, abnormal lipid profiles my lead to cholesterol accumulation in the bone marrow, and thereby reprogram HSPCs towards an active myeloid phenotype, similar to murine studies of atherosclerosis, warranting further investigations in the area (37).

Impact of oxidized and modified lipids and on cellular cholesterol efflux and inflammation
Oxidation of HDL, LDL, and other lipid particles hamper cholesterol transport and induces inflammation. HDL can be oxidized by multiple biological mechanisms, with oxidation by neutrophil and macrophage-released myeloperoxidase (MPO) being the most understood (38). MPO-driven oxidization alters numerous amino acids within ApoA-1, compromising ApoA-1 function which leads to cholesterol accumulation in macrophages (39). ApoA-1 oxidized by nitration reduces the activation of lecithin: cholesterol acyltransferase (LCAT), hampering early steps in reverse cholesterol transport (40). Moreover, NF-kB activation is induced (41). Furthermore, the atherogenic effects downstream of ApoA-1 oxidation are associated with cardiovascular events (42). Like oxidized HDL, oxidized LDL (ox-LDL) is inflammatory and disrupts cholesterol transport. Once phagocytized by macrophages, ox-LDL contributes to cholesterol crystal formation and lysosomal rupture, activating the NLRP3 inflammasome (43). Further, cholesterol delivered by ox-LDL prevents cholesterol efflux in macrophages in a similar lysosomal-dependent manner (44) and causes the downregulation of ABCA1 at both the protein and mRNA levels in vascular endothelial cells (45). Alongside its detrimental effects on cholesterol transport, ox-LDL is directly implicated in atherosclerosis. Through binding to lectin-like oxidized low-density lipoprotein receptor (LOX-1), ox-LDL induces a variety of proatherogenic effects, such as foam cell formation as well as endothelial activation and apoptosis (46). Beyond oxidized HDL and LDL, other modified lipids like lipoprotein (a) (Lp(a)) can disrupt cholesterol efflux and increase inflammation. Lp(a) has a robust inverse association with CEC and directly disrupts plasminogendependent cholesterol efflux (47). Phospholipids within Lp(a) can be oxidized, further increasing its atherosclerotic effects, such as inducing arterial wall and macrophage-driven inflammation (48). These oxidized phospholipids can also carry and dispense MCP-1, further intensifying vascular inflammation (49).

Human models of inflammation and dyslipidemia
Psoriasis is a chronic inflammatory, immune-mediated skin disease affecting 2-3% of the adult US population (50-52).
Psoriasis patients are at high-risk of developing early-onset CAD, with an increased prevalence of non-calcified coronary plaques that are vulnerable to rupture, often leading to MI (3,51,53). In psoriasis, the prevalence of non-calcified coronary burden has a robust correlation with abnormal cholesterol trafficking, evident by impaired CEC, an elevation in circulating neutrophils that are activated, and increased activity in the bone marrow and spleen determined by heightened uptake of fluorodeoxyglucose (FDG) (2, 36, 54). The impairment in HDL function may partially be attributed to the elevation of oxidized LDL and oxidized HDL that are associated with the severity of coronary disease (55). In vitro studies of HDL function showed that macrophages loaded with oxidized LDL did not release cholesterol to HDL (44). Moreover, oxidized LDL accumulation has been reported in psoriatic lesions, most likely due to ineffective removal by HDL (56). Further, in psoriasis, the proteome of HDL various compared to healthy controls, leading to reduced CEC (57). HDL from patients with psoriasis had a lower concentration of ApoA-1 and ApoM. In exchange, the acute-phase proteins prothrombin, alpha-1-acid glycoprotein 1 and serum amyloid A were increased in HDL (57). Moreover, HDL particle size is smaller in psoriasis, which are known to efflux cholesterol less efficiently than their larger HDL counterparts and this finding is associated with aortic vascular inflammation by FDG-PET (20). Similar to murine models of atherosclerosis, psoriasis patients are inordinately inflamed, perpetuating abnormal cholesterol handling that further drives an overactive immune response (37). Currently, it is not known if cholesterol accumulation occurs in psoriasis bone marrow as a result of abnormal HDL function, however, ongoing evidence prompts future studies.
The evidence of interdependent pathways linking cholesterol transport and chronic inflammation extends beyond psoriasis. SLE has similar findings of altered lipid metabolism, with various lipid metabolites, such as arachidonic acid correlating with disease severity (58) and increased HDL oxidation, due to MPO released by neutrophils during NETosis (59). Due to the heightened state of oxidation impairing HDL function, patients with SLE have reduced CEC, which is associated with the increased cardiovascular disease found in SLE patients (60). Further, HDL derived from SLE patients has been shown to promote NF-kB signaling, suggesting SLE HDL can activate the inflammasome, promoting NETosis, further compromising un-modified HDL (61). Low-density granulocytes, a type of ne ut rophil in creased in SLE and associat ed with atherosclerosis, has been shown to have an inverse relationship with CEC, suggesting heightened neutrophil driven impairment of cholesterol trafficking in the disease (62). T-cell activation in SLE is also heightened, in part due to impaired CEC. T-cell lipid raft formation and antigen expression is enabled by dysfunctional ApoA-1 and the inability of HDL to lower both cholesterol and major histocompatibility class II protein levels (63). Impaired CEC in SLE therefore could partially be responsible for increased Tcell activation in SLE (64). As a consequence of increased activation, the presence of ApoA-1 antibodies has been noted in SLE (65). Destruction of ApoA-1 further hampers efflux, and ApoA-1 antibodies have been shown to correlate with SLE disease activity.
Patients with rheumatoid arthritis (RA) also suffer from similar lipoprotein dysfunction. In RA, there is an increased presence of oxidized LDL, possibly due to increased neutrophilic production of ROS (66). Further, similar to psoriasis, CEC is negatively associated with disease severity in RA patients. Interestingly, while there is no significant difference in CEC between RA and controls, there is a stark decrease in CEC between those with major disease, when compared to those with little to no disease activity (67). Further, CEC in RA is negatively associated with MPO levels, comparable to SLE (67). Complementing this, plasma from RA patients was found to increase foam cell formation, downregulating cholesterol efflux proteins such as ABCA1, while upregulating scavenger receptors such as cluster of differentiation (CD)36. Finally, in a study of the synovial fluid lipidome of RA patients, 135 synovial lipids were found to be associated with disease activity and leukocytosis, suggesting a large amount of crosstalk between lipid meditators and inflammatory activity (68). Strikingly, these associations and lipidome changes were shown to occur before disease onset in the preclinical stage, indicating that these lipidome changes are not simply a result of RA induced inflammation (68). The literature shows regardless of the etiology of systemic inflammation, common consequences are HDL dysfunction, failures in cholesterol transport and overall lipid dysfunction.

Inflammation as a therapeutic target
Abnormal cholesterol handling may contribute to the interdependence of inflammation and dyslipidemia and represents a critical area of research to elucidate therapeutic targets in cardiovascular pathologies. While treatment of cardiovascular diseases has benefited from the use of LDLlowering drugs, residual inflammatory risk suggests efforts should be made to target both lipid dysfunction and inflammation. Over 40% of cardiovascular events occur in individuals with normal LDL levels (69), highlighting that isolated efforts to decrease LDL quantities do not remove all cardiovascular risk. This interdependent relationship was further supported in the JUPITER trial. Patients on statin therapy had a reduction in cardiovascular events only if both their LDL and inflammatory C-reactive protein (CRP) levels dropped (5). Finally, the Canakinumab Anti-Inflammatory Thrombosis Outcome Study (CANTOS) was pivotal in showing that targeting inflammasome driven inflammation with canakinumab, a human IgGk monoclonal antibody targeting IL-1b that was developed by Novartis for the treatment of immune disorders, lowered cardiovascular risk (6). Systemic inflammatory conditions provide clinical models to understand how anti-inflammatory therapy may alleviate lipid dysfunction. In a recent study, HDL was isolated from 15 psoriatic patients (at baseline and after anti-psoriatic therapy) and from 15 age-and sex-matched healthy controls (70). Antipsoriatic therapy was associated with improved serum lecithincholesterol acyltransferase activity (LCAT) and improved CEC suggesting that abnormal lipid trafficking in chronic inflammatory conditions is improved upon treatment of inflammation (70). In SLE, a randomized, double-blind, placebo-controlled clinical trial of tofacitinib associated with improved HDL cholesterol levels and particle number, as well as improved CEC (71). Finally, treatment of rheumatoid arthritis reduced inflammation as measured by high sensitivity C-reactive protein, which associated with improved CEC (72). These findings illustrate the potential of solving the challenge of lipid trafficking through the treatment of inflammation and represent a paradigm shift towards a focus on treating inflammation and dysfunctional lipoprotein metabolism as connected entities.

Cholesterol trafficking as a therapeutic target
New treatment efforts to combat dyslipidemia include focusing on cholesterol metabolism and trafficking. Much like treatment of inflammation is associated with improved lipid trafficking, mimetics have also shown to be independently associated with ameliorated lipoprotein metabolism. ApoE mimetic peptide therapy, for example, may be ideally suited for the treatment of hypercholesterolemia and may provide additional benefits when compared with alternatives such as PCSK9 inhibitors (73). Two ApoE mimetic peptides -Ac-hE18A-NH (2) and mR18Lhad a similar reduction in plasma cholesterol and atherosclerotic lesion areas (74). Moreover, ApoA-I mimetic peptides are potential therapeutic agents for increasing CEC (75). More recently, however, there has been interest in the potential of recombinant LCAT in improving cardiovascular disease and abnormal lipoprotein profiles. In thirty ST-segment-elevation myocardial infarction patients, in vitro incubation of plasma with recombinant human LCAT restored the ability of HDL to promote endothelial nitric oxide production, suggesting that LCAT is a potential therapeutic target for restoring HDL function (76). Moreover, infusion of A12 antibodies into mice lowered plaque formation and reduced circulating free LDL (76). These findings suggest that anti-ALDH4A1 antibodies and recombinant LCAT improves lipid trafficking and may have therapeutic efficacy in cardiovascular disease. Indeed, interest in this area has commenced clinical trials to investigate further the potential of such therapeutics, such as REAL-TIMI 63B, a phase 2b randomized study to evaluate the efficacy, safety, pharmacodynamics, and immunogenicity of repeat doses of MEDI6012 in adult subjects presenting with acute STEMI. Another field of growing interest, is the use of genetic studies to elucidate associations between rare gene variants and dyslipidemia, thus providing pharmacological targets. For example loss-of-function variants in the ANGPTL3, a lipoprotein lipase inhibitor, leads to lower plasma levels of LDL-cholesterol and triglycerides (77), concomitant with reductions in coronary artery disease (67). Therefore, ANGPTL3 is currently a pharmacological target for the treatment of cardiovascular disease (CVD) (78). Experimental evidence demonstrates that anti-ANGPTL3 therapies have a significant lipid lowering effect from phase I clinical trials with an anti-ANGPTL3 antibody (evinacumab) (79) and anti-sense oligonucleotide targeting ANGPTL3 (80). However, it remains undetermined if this lipid lowering therapy decreases cardiovascular events.

Conclusion
Future efforts should be directed to further understand the interplay between inflammation and cholesterol handling and expand upon the nascent clinical studies implicating dysfunctional cholesterol trafficking as a cause of immune cell expansion. Treatment strategies for cardiovascular disease and systemic inflammatory conditions should begin to treat dyslipidemia and inflammation as connected entities rather than two distinct pathologies. Further work is needed to parse out the role CEC plays in humans to help mediate these complex relationships.

Author contributions
RO'H, NM and HT were involved in designing the concept of the review and oversight. RO'H, AB and HT were involved in the literature search, summation of the literature, and revisions of the manuscript. RO'H, AB, CH, PP, and HT drafted the manuscript. All authors contributed to the article and approved the submitted version.

Funding
Supported by the National Heart, Lung, and Blood Institute Intramural Research Program (HL006193-07). This research was made possible through the NIH Medical Research Scholars Program; a public-private partnership supported jointly by the NIH and contributions to the Foundation for the NIH from the Doris Duke Charitable Foundation, Genentech, the American Association for Dental Research, the Colgate-Palmolive Company, and other private donors.

Conflict of interest
NM is a full-time US government employee and has served as a consultant for Amgen, Eli Lilly, and Leo Pharma, receiving grants/other payments; as a principal investigator and/or investigator for AbbVie, Celgene, Janssen Pharmaceuticals, Inc, Novartis, and AstraZeneca receiving grants and/or research funding; and as a principal investigator for the National Institute of Health receiving grants and/or research funding.
The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher's note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.